The resurfacing of the seating surface on poppet valves for internal combustion engines has typically required utilization of cumbersome and expensive machinery which effects a grinding of the seating surface. Such machinery is not only expensive to purchase and maintain, but is also complex to operate. Small repair shops generally cannot afford such machinery, and hence will often replace the valve due to an inability to efficiently refinish the seating surface of the old valve.
To provide a simple and inexpensive tool for refacing of poppet valves, U.S. Pat. No. 4,637,762, owned by the assignee hereof, discloses a valve refacing device employing a cylindrical sleevelike housing having a conical recess formed in one or both ends thereof. One or more carbide cutting blades are mounted on the housing so as to project outwardly from a conical surface defining the conical recess. With this device, the poppet valve is positioned so that the stem projects coaxially through a clearance opening provided in the housing, whereupon the valve seating surface is positioned within the recess for engagement with the cutting blades. Relative rotation between the device and the poppet valve effects cutting, and hence refacing, of the seating surface. This device can be readily manufactured to accommodate different valve seat angles.
While the device of U.S. Pat. No. 4,637,762 performs a desirable valve refacing operation, nevertheless this device does possess inconveniences. For example, the free end of the valve stem is typically gripped by a vise to stationarily support the valve, following which the device is manually gripped and axially pulled toward the valve head to control the contact pressure between the cutting blades and the valve face, whereupon manual rotation of the device then effects desired refacing of the valve face. Gripping the valve stem by the rough vise surfaces may, however, damage the valve stem. Also, the contact pressure between the cutting blade and the valve face is controlled by the operator pulling on the device at the same time he is rotating it, and it is difficult to apply an even pressure while at the same time turning the device at a uniform rotational speed. Further, when a small-diameter valve is refaced, the unsupported length of the valve stem can lead to valve tipping in the conical recess if the operator relaxes the contact pressure, which can then result in uneven cutting.
There is thus a need for a manual valve resurfacing device that can readily hold a valve without damage and that can apply an even pressure between the cutting blade and valve face while the cutting blade is being rotated. The present invention relates to an improved valve refacing device which is believed capable of performing in this manner, and hence overcomes the disadvantages associated with prior devices.